Aim: To study the effect of 5-nitro-2-fumldehyde semicarbazone (nitrofurazone), a derivative of nitrofuran, onmale reproductive organs of Parkes (P) swain mice. Methods: Mice were given nitrofurazone orally at a dose of 64mg/kg body weight per day, for 10 and 20 days, and were killed 24 h and/or 56 days after the last treatment. Histo-logical appearance of testis, motility and number of spermatozoa in cauda epididymidis, and biochemical indices in epi-didymis and seminal vesicle were evaluated. Results: Histologically, testis showed marked regressive changes inthe seminiferous tubules in mice treated with nitrofurazone. Ten days after treatment, there was much depletion of germcells in the seminiferous tubules, and the germinal epithelium was lined mainly with Sertoli cells, spermatogonia, sper-matocytes, and a few round spermatids; intraepithelial vacuoles and multinucleated giant cells were also observed intubules. By 20 days, regressive changes in the seminiferous tubules were further pronounced, and Aim: To study the effect of 5-nitro-2-fumldehyde semicarbazone (nitrofurazone), a derivative of nitrofuran, onmale reproductive organs of Parkes (P) swain mice. Methods: Mice were given nitrofurazone orally at a dose of 64 mg / kg body Histo-logical appearance of testis, motility and number of spermatozoa in cauda epididymidis, and biochemical indices in epi-didymis and seminal Results: Histologically, testis showed marked regressive changes inthe seminiferous tubules in mice treated with nitrofurazone. Ten days after treatment, there was much depletion of germ cells in the seminiferous tubules, and the germinal epithelium was lined mainly with Sertoli cells, spermatogonia , sper-matocytes, and a few round spermatids; intraepithelial vacuoles and multinucleated giant cells were also observed intubules. By 20 days, regressive changes in the seminiferous tubules were furth er pronounced, and